Method of lens grinding



March 1, 1966 K. D. FAAS ETAL 3,237,349

METHOD OF LENS GRINDING Filed Jan. 2, 1963 5 Sheets-Sheet 1 1H7. .1 III B 66L; my I 'M 9 B .M

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5 I} w I9 3 4 6 R l l// L "I KENNETH D. FAAS ISRAEL SCHRIER 1 NV TORS wfiag March 1965 K. D. FAAS ETAL METHOD OF LENS GRINDING 5 Sheets-Sheet 2 Filed Jan. 2, 1963 KENNETH D. FAAS ISRAEL SCHRIER 1N ENTORS F 4 5 Sheets-Sheet 5 KENNETH D. FAAS ISRAEL SC HRIER A'JI'IYO IRNIEYS March 1, 1966 K, D. FAAS ETAL METHOD OF mus GRINDING Filed Jan. 2, 1963 FIG. 5

FIG. 6

3% fink/P.

United States Patent 3,237,349 METHOD OF LENS GRINDHNG Kenneth D. Faas, Henrietta, and Israel Schrier, lroudequoit, N.Y., assignors to Bausch 8: Lomb Incorporated, Rochester, N.Y., a corporation of New York Filed Jan. 2, 1963, Ser. No. 249,050 3 Claims. (Cl. 51284) This invention rel-ates to ophthalmic lenses and more particularly to a method of generating a surface on an ophthalmic lens.

The conventional ophthalmic lens sold by the industry is a semi-finished lens blank. One of the major surfaces is usually finished and the other major surface is unfinished as the prescription is usually ground on this surface. A surface generating machine is used to generate the unfinished surface of the lens which is subsequently polished to complete the surfacing of the major surfaces of the lens blank. According to conventional practice the generating of the second major surface of the lens blank requires considerable calipering and measuringto arrive at the predetermined prescription for the lens. This practice is time consuming and expensive and accordingly this invention deals with a method which substantially reduces the time and effort required for finishing the lens blank and yet retains the accuracy required of the surfaces for a salable lens.

The invention provides for blocking a lens with at least one reference surface which is subsequently used in a surfacing operation to control the relationship of the second surface relative to the finished surface. This process eliminates the need for calipering used in conventional standards.

It is an object of this invention to provide a lens surfacing process.

It is another object of this invention to automatically control the relative position of the first major surface on a lens blank during the generating of the second major surface of the lens blank to thereby provide the desired optical characteristics of the finished lens.

It is a further object of this invention to block a lens with a lens block surface oriented in a predetermined relationship relative to a first major surface on the ophthalmic lens and utilize this relationship to generate a second major surface on the lens during a subsequent machining operation to thereby produce the desired optical characteristics.

It is a further object of this invention to establish a reference surface on the lens block while molding the lens block on a finished major surface and utilize this relationship of surfaces in generating a second major surface on the lens to thereby provide an ophthalmic lens of the desired optical characteristics.

The objects of this invention are accomplished by mo1ding a reference surface on a lens block simultaneously with molding of the block on the lens. More than one reference surface may be molded on the lens block during the molding operation to insure accuracy in the subsequent surface generating operation.

A subsequent operation which includes generating of a second major surface of a prescribed curvature relative to the first major surface provides the desired optical characteristics. The relationship of the second major surface relative to the first major surface is controlled in such a manner that corrections for astigmatic defect, prismatic defect, and spherical defect of the eye may be corrected in the finished lens. The combination of these optical characteristics are controlled by the selection of a lens blank of the desired toric surface and adjusting the lens relative to the molding cavity to mold the reference surface of the lens block to adjust for spherical and pris 3,237,349 Patented Mar. 1, 1966 matic correction required in the finished lens. The necessity of calipening the lens during the subsequent surface generating step is eliminated as the reference surfaces of the lens block control the surface to be ground as the second major surface of the lens blank. The molding of the lens block may be the complete molding of the block or a bonding process which bonds the lens to an insert having the desired reference surfaces preformed on the insert.

The following description and the attached drawings illustrate the preferred embodiment of this invention.

FIG. 1 illustrates a cross-section view of the lens positioned on the mold.

FIG. 2 illustrates the step of molding the lens block.

FIG. 3 illustrates the lens blank having a lens block molded thereto with a portion cut away to illustrate the relationship of the reference surfaces relative to the finished surface on a semi-finished lens blank.

, FIG. 4 illustrates an exploded view of the mechanism required for the polishing operation of the lens blank.

FIG. 5 illustrates a side view of a surface generating machine.

FIG. 6 illustrates the plan view of a surface generating machine.

Referring to FIG. 1 the lens 1 is positioned on the mold for forming the lens block. The mold is supported on a base member 2 which supports the sleeve 3. The arm 4 is pivotally supported on the base 2 and is pivotally connected to the collar 5. The bolts 6 pivotally connect the arm 4 by means of the bushings 7 to the collar 5.

The sleeve 3 supports a seal 8 which engages the lens 1. A plurality of pins 9 engage the lens 1 on their upper end and seat on the prismatic adjustment ring 10. The ring 10 is pivotally supported on the ears 11 by the needle bearings 12. The ear 11 is integral with the bracket 13. The bracket 13 is received within a recess on the outer periphery of the sleeve 3 and is axially rotatable about the sleeve 3 to provide the prismatic adjustment of the lens 1 by tilting .the ring 10. The adjusting screw 14 slides the cam 15 in a radial manner'to tilt the ring 10 .and accordingly tilt the lens 1. I

The plunger 16 is non-rotatably mounted within the sleeve 3. The plunger 16 slidably moves within the sleeve 3 in response to movement of the lever 4. A central opening within the plunger 16 receives the pin 17. The uppermost end of the pin 17 engages the vertex of the lens 1 thereby controlling the plunger position axially relative to the lens prior to molding. The plunger 16 is then locked by the set screw 18 in the key slot 19. As the plunger is locked in position the pin 17 is released and moves downward into the position as shown in FIG. 2. The plunger 16 remains fixed in this position and controls the molding of the surface on the lens block.

The lens 1 is retained in position by lowering the ram 20 causing the plurality of fingers 21 to engage the lens 1 on the opposite side of the lens from the pins 9. The ram 20 is locked in this position relative to the lens. FIG. 2 illustrates the fixed position on the mold and the pin 17 retracted to its lower position. The fingers 21 are engaging the upper portion of the lens maintaining a lens in a fixed position on top of the mold. A supply of molten metal is retained within the chamber 23 of the tank 24. The valve handle 25 is moved forwardly and rotated so that the nozzle 26 is received within the opening 27. The metal flows from the chamber 23 into the mold cavity 28. When the mold cavity 28 is filled the handle is rotated until the lens block in the mold cavity 28 hardens and then the handle is retracted.

FIG. 3 illustrates the molded lens block 30 molded on the lens blank 1. The semi-cylindrical surface 31 is formed on the end of the lens block 30. The surface 31 is a predetermined axial distance X from the vertex 32 on the first major surface of the lens. The planar surface 33 is also in a fixed radial distance Y to the bottom of the semi-cylindrical surface 31. The axis about which the semi-cylindrical surface 331 is generated lies in the planar surface 33. The radius Z is a standard dimension used in the chuck of the surface generating machine. The arrows indicating these dimensions illustrate the relationship of these surfaces relative to the vertex on the first major surface on the lens blanks 1.

The lens block on the lens 1 is also illustrated in FIG. 4 prior to positioning on the fitting 36. The fitting 36 is operated by the motor 37. A polishing lap 38 polishes the unblocked major surface of the lens 1.

Referring to FIGS. 5 and 6 the surface generating machine is shown whereby the lens blank 1 is positioned in the chuck of the surface generating machine. A semicylindrical element 40 is received within the semi-cylindrical slot 31 as the clamp 42 locks the lens block 30 in place. The grinding wheel 43 is rotated by the motor 44.

The motor 44 is in fixed relationship to the frame 59 of the machine. The chuck 45 is, however, movable relative to the frame 59 by the adjusting mechanism 46. The thumb screw 47 is connected to a screw portion which moves the slide 48 in the slot 49. The movement is indicated by the point 50 relative to the scale 51. An additional adjustment is usually provided on the chuck to the length of the radius arm between the pivot point 68 and the cutting surface of the grinding wheel to change the curvature of the surface ground on the second major surface of the lens.

A second adjustment is provided by the thumb screw 52 which is connected to the screw portion 53 operating within the bracket 54. The screw 53 moves the slide 55 in the keyway 56 to provide an adjustment normal to movement created by the screw 47. These screws move the pivoting axis of the arm 58 relative to the frame 59.

The pivoting action of the arm 58 permits the insertion of the lens block 30 and the lens 1 by swinging the chuck 45 out of alignment with the grinding wheel 43.

The relationship of the surface 31 in the lens block 30 is indicated in a direct reading on scale 60 and a Vernier 61. This reading controls the axial distance of this surface relative to the vertex of the lens 1. By the use of this established relationship of surfaces the surface generating [machine illustrated in FIGS. 5 and 6 can be set to generate the desired second major surface on the lens blank relative to the first major surface of the lens blank upon which the lens block is attached.

The method for grinding lenses operates in the following described manner. The first step includes positioning of the lens 1 on the mold in a predetermined position. The ram 20 is then lowered to retain the lens in position on the mold. The prismatic adjusting ring 10 is adjusted by the cam 15 responsive to the screw 14 to provide the desired prismatic correction. The tilting of the ring 10 tilts the lens 1 in a direct relationship. Four pins 9 are spaced approximately 90 from each other within the mold 65 in a manner so that the lens engages the pins for tilting a spherical or toric lens in a like manner. In the case of a toric lens it is positioned with the pins essentially equally distant from meridians at maximum and minimum curvature on the lens to tilt the lens in accordance with the tilting of ring 10. The pin 17 is then moved upwardly carrying the plunger 16 to engage the vertex on the surface of the lens. The plunger 16 is then locked in position by the set screw 18. Upon release of the pin 17 the pin retracts to the position as indicated in FIG. 2.

The established relationship of the surface formed by the semi-cylindrical element 66 is maintained in this position even though the pin 17 is retracted from its contacting position with the vertex of the lens.

The lens block 30 is then molded on the lens 1 as indicated in FIG. 2. The surfaces 31 and 33 molded on the lens block bear a constant dimensional relationship relative to each other and to the point 32 on the first major surface of the lens. The position of the block per se is varied relative to the lens in accordance with the prescription to be ground on the lens. Subsequent to molding of the lens block 39 on the lens 1, the lens block and lens are removed from the mold 65. FIG. 3 illustrates the block 30 and lens element 1 integral with each other. The lens block 30 and lens 1 is then positioned in the chuck 45 and locked in position with a semi-cylindrical insert as received within the mating semi-cylindrical slot 31. The axial dimension from the vertex 32 on the major surface 41 of lens 1 to the second major surface ground On the lens is indicated by the scale 61. The predetermined lens thickness is set by moving the chuck 45 and aligning the Vernier 61 within the scale 60.

The adjusting screws 52 and 47 are set to generate the desired surface curvature to be ground on the lens by moving the pivot point 68. The surface generating machine then grinds the desired lens thickness and surface on the second major surface of the lens 1. I

The polishing operation is subsequent to the grinding operation and illustrated in FIG. 4. The insert 36 is received within the semi-cylindrical slot 31 as the lens block 39 is placed in the polishing machine. The motor provides motion necessary for surfacing the lens. The lens 1 is then polished to provide the finishing step in the lens surfacing process. The semi-cylindrical recess in conjunction with the extended tapered center port-ion 70 are used for toric and spherical surfacing respectively. The semi-cylindrical recess provides greater bearing surface which consequently results in less wear and maintains better alignment.

The prior description and illustration sets forth the preferred embodiment of this invention, the scope of which is defined in the attached claims.

We claim:

1. The method for generating a major surface on a lens having one finished major surface comprising the steps, aligning the lens with a finished surface of the lens engaging the lens supporting means of a lens block mold with the axis of the mold passing through a point defining the vertex of the finished surface of the lens, molding a lens block on the finished surface of the lens while simultaneously forming a reference surface on the lens block a predetermined axial distance from the vertex of the finished surface of the lens, placing the blocked lens in a pivotally supported chuck of a surface generating machine with the vertex of the finished surface of the lens defining an are when said lens is pivoted with the chuck and which are includes the cutting surface of the grinding wheel, setting the location of the arc defined by the vertex on the finished surface of the lens a predetermined distance from the cutting surface of the grinding wheel which is equal to the lens thickness, and automatically generating the second major surface on the lens to form a lens of predetermined thickness and optical characteristic.

2. The method of generating a major surface on a lens having one finished toric major surface comprising the steps, aligning a lens on a lens block mold with the axis of the mold passing through a point defining the vertex of the finished surface of the lens, molding a lens 'block on the finished surface of the lens and simultaneously forming at least one reference surface a predetermined axial dimension and orientation from the vertex of the finished lens surface, placing the blocked lens in a chuck of a surface generating machine with the vertex of the finished surface defining an arc in response to pivotal movement of the chuck relative to the cutting surface of the grinding Wheel, spacing the position of the arc defined by the vertex relative to the cutting surface of the grinding wheel an increment equal to the lens thickness, automatically generating the second major surface of the lens as the chuck pivots relative to the cutting surface of the grinding wheel thereby providing a lens of the desired thickness and optical characteristic.

3. The method of generating a major surface on a lens having a finish convex major surface comprising the steps, aligning the lens with the vertex of the finished major surface in axial alignment relative to the lens block mold and a predetermined axial dimension relative to a reference surface forming element in the lens block mold, forming a metallic lens block on the finished surface of said lens While simultaneously forming the reference surface a predetermined axial dimension and orientation from the vertex of the finished surface of the lens, placing the lens block and lens in a chuck of a surface generating machine With the vertex of the finished surface of the lens cutting surface of the grinding Wheel, setting the radial location of the arc defined by the vertex of the finished surface of the lens a radial increment equal to the desired lens thickness from the cutting surface of the grinding Wheel, automatically generating the second major surface on the lens to thereby provide a lens of predetermined thickness and optical characteristic.

References (Cited by the Examiner UNITED STATES PATENTS 1,911,153 5/1933 Hill 5l-284 3,049,766 8/1962 Buckminster 2258 3,118,198 1/1964 Prunier 51-277 X defining an are when the chuck is pivoted relative to the 15 LESTER M. SWINGLE, Primary Examiner. 

1. THE METHOD FOR GENERATING A MAJOR SURFACE ON A LENS HAVING ONE FINISHED MAJOR SURFACE COMPRISING THE STEPS, ALIGNING THE LENS WITH A FINISHED SURFACE OF THE LENS ENGAGING THE LENS SUPPORTING MEANS OF A LENS BLOCK MOLD WITH THE AXIS OF THE MOLD PASSING THROUGH A POINT DEFINING THE VERTEX OF THE FINISHED SURFACES OF THE LENS, MOLDING A LENS BLOCK ON THE FINISHED SURFACE OF THE LENS WHILE SIMULTANEOUSLY FORMING A REFERENCE SURFACE ON THE LENS BLOCK A PREDETERMINED AXIAL DISTANCE FROM THE VERTEX OF THE FINISHED SURFACE OF THE LENS, PLACING THE BLOCKED LENS IN A PIVOTALLY SUPPORTED CHUCK OF A SURFACE GENERATING MACHINE WITH THE VERTEX OF THE FINISHED SURFACE OF THE LENS DEFINING AN ARC WHEN SAID LENS IS PIVOTED WITH THE CHUCK AND WHICH ARC INCLUDES THE CUTTING SURFACE OF THE GRINDING WHEEL, SETTING THE LOCATION OF THE ARC DEFINED BY THE VERTEX ON THE FINISHED SURFACE OF THE LENS OF PREDETERMINED DISTANCE FROM THE CUTTING SURFACE OF THE GRINDING WHEEL WHICH IS EQUAL TO THE LENS THICKNESS, AND AUTOMATICALLY GENERATING THE SECOND MAJOR SURFACE ON THE LENS TO FORM A LENS OF PREDETERMINED THICKNESS AND OPTICAL CHARACTERISTIC. 